Unmasking tracks, adding Trash distortion and matching a track’s sound with that of an instrument? iZotope Neutron 4 makes it easy

Neutron 4’s new features all build on the machine learning algorithms that are now at the core of all iZotope products I have reviewed. Neutron is a mixing plug-in and its AI-powered Mix Assistant no longer asks questions before it starts analysing your track. It comes with a new Assistant View that is much better than the previous version’s. The Assistant starts listening as soon as you play audio. It produces a reference starting point, like the old one. The resemblance ends there, though. Once you have your starting point, which in my tests was faster than with the old version, you’ll be taken to a control center where you can perfect your sound or associate it with an instrument from a list of presets or one that you sampled.

The new Intent Controls make sonic improvements by dialling in punch (related to the Compressor module) and distortion (referring to the Exciter module) to taste, leaving the Detail View the last frontier if you need to fine tune. I assume the need to will differ from one project to the next, but in my tests I rarely needed to actively change the assisted changes on a decent mix to obtain better results.

The reference matching you can perform — in real time — lets you dynamically match the tone of your track to a sample or stem using a Target Library with tone matching technology. With one click, Neutron loads stem references into your Target Library to enable the Assistant to match drums, bass, guitar, vocal, or audio tracks to the sound you are going for.

The Target Library contains hardwired presets, but you can build your own Targets with stems and sounds. A minor frustration (or is this an oversight?) is that the Open dialogue pointed to my system disk’s root folder.

For this review, I created a sound snippet using a felt piano from the SINE Player library plug-in and used that as a target for the SINE Player Grand Piano in a mix where the latter sounded harsh due to modulation with other tracks. My idea was to shave off the Grand Piano’s cold sounding extremes by using Neutron’s Target capabilities.

The only thing I can say is that it worked better than I expected. The result didn’t sound like it was muffled but combined the clarity of the Grand with the softness of the felt piano. The more I dragged the Intensity slider to the 100% mark, the more the Grand’s harsh explosions were pushed into the background, making for a more pleasant mix. The entire process, including the bouncing of a track with a few notes on the felt piano, took me less than 10 minutes to complete.

Another feature that has been improved is Unmasking. You can use Unmask from a track or a bus, then adjust levels to reach the optimal balance. This works well with a mix that is somewhat balanced. With mine, though, I made the mistake to have very low velocity on the low notes of the Grand Piano with cellos playing in the background. The result was a small part of the Grand’s region where the piano is barely audible.

I tried solving that problem with Unmasking, but that unmasked the rest of the Grand as well, resulting in a track that globally was too loud. The alternative I came up with was to use Unmask on a split of the two track regions and that worked well. I tried another alternative, which was to automate the volume but the changes had to be so abrupt that it became ridiculous.

The Exciter Module in Neutron 4 now has Trash 2 to distort and destroy sound with Trash Mode. Trash is a lot of fun and makes it easy to discover extremes in sound textures. Personally, I don’t like to go to extremes, but with Trash 2 a slight move can make a dull sound become interesting.

Character changes can be tuned with a new Tone Slider. A Tame button preserves dynamic expression as you destroy.

As with the previous version, Neutron 4 comes with its Visual Mixer which is a boon to improve the stereo image of your Neutron-enabled tracks. The plug-ins communicate with each other through iZotope’s own communication protocol, without you having to do anything
special to make it work.

Finally, Neutron 4 comes with a scope for your sidechain. It lets you visualise the changed dynamics with a new Oscilloscope View in Neutron’s Compressor. You can use the Oscilloscope View after setting up your sidechain to see your sound as you dial in the changes.


I’ve yet to be disappointed by iZotope and Neutron 4 is yet another upgrade that improves what was available in the previous version while adding new features with useful functionality. Those are clearly not meant to create the illusion that the upgrade is worth its money. They make your work easier and allow you to focus more on the creative side of things.

Neutron 4 doing all this without making my old machine run slower than it usually does is no small feat. The new version is available from iZotope’s website for $299.

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